1. Field of the Invention
The present invention relates to an information recording medium such as paper on which multimedia information, including audio information such as speech and music, video information obtained from cameras and video apparatuses, and digital code data obtained from personal computers and word processors, is recorded as an optically readable code pattern.
2. Description of the Related Art
Various types of mediums, such as a magnetic tape and an optical disk, have been conventionally known as mediums for recording speech, music and the like. These mediums require a large space for keeping themselves and their unit costs are somewhat expensive, even though a great number of copies are made. To move a medium on which audio information is recorded to a person in a remote place takes a lot of time and labor whether it is mailed or handed. These problems are true of all the multimedia information including video information obtained from cameras and video apparatuses and digital code data obtained from personal computers and wordprocessors in addition to the audio information.
The team of engineers including the inventor of the present invention conceived a system for recording multimedia information including at least one of audio information, video information and digital code data, on an information recording medium such as paper in the form of a dot code as image information, i.e., coded information which can be facsimiled and copied in great numbers at low cost and for reproducing the multimedia information from the information recording medium, and filed an invention of the system as U.S. patent application Ser. No. 08/407,018.
The U.S. Patent Application discloses a group of blocks arranged in matrix. Each of the blocks has a data dot pattern formed of a plurality of dots arranged in accordance with data and a block address pattern indicating an address of the block and located in a predetermined position with respect to the data dot pattern.
More specifically, as shown in FIG. 1A, each block includes markers 10, arrangement direction detecting codes 12, a distinctive block address 14, and in-block recording data 16. The markers 10 are each recorded as a large round dot, and the recording data 16 is constituted of dots which are remarkably smaller than the markers 10.
Such blocks are arranged two-dimensionally to form a dot code, as illustrated in FIG. 1B. In this dot code, two blocks are arranged in a vertical direction, while N/2 blocks are done in a horizontal direction. Data is thus reproduced as one code from all the blocks arranged two-dimensionally. In FIG. 1B, the distinctive block address 14 is represented as blocks 1 to N. Each of the blocks has a block width BW in its vertical direction and a block length BL in its horizontal direction, and the width of two blocks corresponds to that of the dot code, called an effective code width CEW.
FIG. 1C simply shows the constitution of the dot code of FIG. 1B using the block address 14 only.
According to the system disclosed in the foregoing U.S. Patent Application, a dot code is optically read and reproduced from an information recording medium by manually moving an information reproduction apparatus to scan the dot code on the information recording medium.
For example, as shown in FIG. 2, a dot code 18 can be manually scanned in its longitudinal direction with the information reproduction apparatus such that a reading unit 20 of the apparatus vertically contacts the dot code 18, i.e., the face of the information recording medium. Since the dot code 18 includes the block address 14, it can be read even though the information reproduction apparatus is moved in any direction. In other words, information recorded as the dot code 18 can be reproduced by manually scanning the dot code 18 from one end to the other with the reading unit 20.
Since, as illustrated in FIG. 2, the reading unit 20 is provided with a scan position indicating mark 22 corresponding to the width of the dot code 18, an operator can correctly perform a manual operation for scanning the reading unit 20 while looking at the mark 22, that is, while paying attention to the width of the dot code 18.
As the information reproduction apparatus for reproducing the dot code 18, U.S. patent application Ser. No. 08/532,982, filed by the same inventor as that of the present invention, discloses a similar one having the constitution as shown in FIG. 3.
The information reproduction apparatus shown in FIG. 3 reads a dot code 18 recorded on a sheet (information recording medium) 24 by scanning a reading unit 20 having an image pickup unit 26 and processes an output signal of the image pickup unit 26 by a processing unit provided separately from the reading unit 20, thereby to reproduce the original multimedia information. It is needless to say that the processing unit can be incorporated into the reading unit 20. The processing unit includes an image unit block data reproduction unit 28, a block link unit 30, and a deinterleave and error correction unit 32. A plurality of images picked up by the image pickup unit 26 in accordance with the manual scanning, are processed by the image unit block data reproduction unit 28 to restore block data. The block data are rearranged by the block link unit 30 based on a block address added thereto for each block, and their errors are corrected by the deinterleave and error correction unit 32. The error-corrected data are output from an output unit 34 as multimedia information such as sound and image.
The image pickup unit 26 has a light for image pickup and is constituted so as to prevent light from being supplied externally. Since the unit 26 picks up an image in a short period of exposure time for every image pickup period of an image pickup element, a blur due to scanning is lessened.
In manual scanning, a scanning speed generally varies from operator to operator. One operator scans slowly, while another does quickly. In the slow scanning, the block link unit 30 processes the blocks whose images are picked up overlappingly and selects one from among the blocks in order to use data of the finally-obtained block or data with the least error when the blocks of the same address overlap one another. Thus, all the blocks are linked, and the original multimedia information is reproduced without any error.
On the contrary, in the quick scanning, some blocks are not imaged. If a number of blocks are not imaged, the original multimedia information cannot be correctly reproduced even though an error is corrected by the deinterleave and error correction unit 32.
The above manual scanning will be described by way of the dot code of blocks as shown in FIG. 4A. In this example, the width of an image pickup area 26A is three times or greater than the width BW of each of the blocks, and the length thereof is also three times or greater than the length BL of each block.
If the dot code is scanned by an information reproduction apparatus having the image pickup area 26A, the image pickup range is shifted as shown in FIG. 4B. In this figure, the solid line indicates the blocks of the dot code and the dotted line represents a one image pickup range. The blocks of block addresses 1 and 2 are imaged in the first image plane, those of addresses 3 to 6 are done in the second image plane, those of addresses 8 to 10 are done in the third image plane, and those of addresses 11, 12, . . . are done in the fourth image plane. If the blocks of all the addresses are imaged in this manner, the original multimedia information can be reproduced with reliability.
If, however, the scanning is performed at high speed, the blocks of addresses 1 and 2 are imaged in the first image plane and those of addresses 7 to 10 are done in the second image plane, but those of addresses 3 to 6 are not imaged, as shown in FIG. 4C. Thus, the original multimedia information cannot be reproduced.